Reference picture resampling activation in video coding

Abstract

Methods, apparatus, systems for video processing, including video encoding or video decoding are described. One example method includes performing a conversion between a video comprising a video picture that includes a video slice and a bitstream of the video. The bitstream conforms to a format rule specifying that, in case a slice type of the video slice is type P and temporal motion vector prediction is enabled, usage of reference picture resampling (RPR) for a reference picture in a collocated reference picture list is disabled. The reference picture is indicated by a reference index of a collocated picture of the video slice used for the temporal motion vector prediction.

What is claimed is: 
     
       1. A method of processing video data, comprising:
 performing a conversion between a video comprising a video picture that includes a video slice and a bitstream of the video; 
 wherein the bitstream conforms to a format rule, and 
 wherein the format rule specifies that, in case a slice type of the video slice is P and a temporal motion vector prediction for the video picture is enabled, usage of reference picture resampling (RPR) for a reference picture in a specific collocated reference picture list is disabled, wherein the reference picture is indicated by a first syntax element, which specifies a reference index of a collocated picture used for the temporal motion vector prediction, and 
 wherein the format rule further specifies that a value of first certain information in a slice header for the video slice indicates the collocated picture used for the temporal motion vector prediction is derived from a reference list 0 when the slice type of the video slice is P and a value of a third syntax element in a picture header of the video picture indicates that the temporal motion vector prediction is enabled for the video picture. 
 
     
     
       2. The method of  claim 1 , wherein the specific collocated reference picture list is the reference picture list 0,
 wherein in case the slice type of the video slice is P and the temporal motion vector prediction for the video picture is enabled, a value of the first syntax element is in a range of 0 to a maximum reference index for the reference picture list 0 allowed to be used to the video slice, inclusive. 
 
     
     
       3. The method of  claim 1 , wherein the specific collocated reference picture list is determined based on a value of a second syntax element in a slice header of the video slice, and the second syntax element indicates whether the collocated picture used for the temporal motion vector prediction is derived from a reference picture list 0,
 wherein the value of the second syntax element is inferred to be equal to 1 in case the slice type of the video slice is P and the temporal motion vector prediction for the video picture is enabled, wherein the value of the second syntax element being equal to 1 indicates that the collocated picture used for the temporal motion vector prediction is derived from the reference picture list 0, and 
 wherein when the value of the second syntax element is equal to 1, the reference picture list 0 is determined as the specific collocated reference picture list. 
 
     
     
       4. The method of  claim 1 , wherein the format rule further specifies whether the value of the first certain information in the slice header for the video slice is inherited from the picture header for the video picture is determined at least based on the slice type of the video slice and a value of a fourth syntax element indicating whether reference picture list information is present in the picture header, or
 wherein the format rule further specifies that the value of the first certain information in the slice header for the video slice indicates that the collocated picture used for the temporal motion vector prediction is derived from the reference list 0 when the slice type of the video slice is P, the value of the third syntax element in the picture header of the video picture indicates that the temporal motion vector prediction is enabled for the video picture and a value of the fourth syntax element indicates that the reference picture list information is present in the picture header, or 
 wherein the format rule further specifies that a value of a fifth syntax element in the slice header of the video slice, which specifies a reference index of the collocated picture used for the temporal motion vector prediction, is in a range of 0 to a maximum reference index for the reference list 0 allowed to be used to the video slice, inclusive, when the slice type of the video slice is P and the temporal motion vector prediction is enabled, or 
 wherein the format rule further specifies that a value of the fifth syntax element in the slice header of the video slice, which specifies the reference index of the collocated picture used for the temporal motion vector prediction, refers to an entry in the reference list 0 and is in the range of 0 to the maximum reference index for the reference list 0 allowed to be used to the video slice, inclusive, when the slice type of the video slice is B and the value of the first certain information in the slice header for the video slice indicates the collocated picture used for the temporal motion vector prediction is derived from the reference list 0. 
 
     
     
       5. The method of  claim 1 , wherein the video picture includes one or more subpictures,
 wherein the format rule further specifies that a sixth syntax element is selectively present in a sequence parameter set of the bitstream based on a number of subpictures in the video picture; and 
 wherein the sixth syntax element indicates whether an in-loop filtering operation is allowed to be performed across subpicture boundaries in a coded layer video sequence (CLVS) and whether all subpicture boundaries in the CLVS are treated as picture boundaries. 
 
     
     
       6. The method of  claim 5 , wherein the format rule further specifies that in case the number of the subpictures in the video picture is 1, the sixth syntax element is not present in the sequence parameter set, and a value of the sixth syntax element is inferred to be equal to 1, and wherein in case the value of the sixth syntax element is inferred to be equal to 1, all subpicture boundaries in the CLVS are treated as picture boundaries and no in-loop filtering operation is performed across subpicture boundaries, or
 wherein the sixth syntax element comprises sps_independent_subpics_flag, or 
 wherein the number of subpictures in the video picture is indicated by a seventh syntax element in the sequence parameter set, which plus 1 specifies the number of subpictures in each video picture in the CLVS. 
 
     
     
       7. The method of  claim 5 , wherein the format rule further specifies that the number of subpictures in the video picture determines a manner of indicating an eighth syntax element, which indicates whether a subpicture of each video picture in the CLVS is treated as a picture in the conversion excluding the in-loop filtering operation,
 wherein in case the number of subpictures in the video picture is 1, a value of the eighth syntax element is inferred to be equal to 1, and 
 wherein in case the value of the eighth syntax element is equal to 1, a subpicture of each video picture in the CLVS is treated as a picture in the conversion excluding the in-loop filtering operation, or 
 wherein the format rule further specifies that the number of subpictures in the video picture determines a manner of indicating a ninth syntax element, which indicates whether the in-loop filtering operation is allowed to be performed across subpicture boundaries, 
 wherein in case the number of subpictures in the video picture is 1, a value of the ninth syntax element is inferred to be equal to 0, and 
 wherein in case the value of the ninth syntax element is equal to 0, the in-loop filtering operation across subpicture boundaries is disabled. 
 
     
     
       8. The method of  claim 1 , wherein the video picture includes one or more subpictures,
 wherein the format rule further specifies that a value of a tenth syntax element indicating whether each of the one or more subpictures in the video picture consists of a single slice is determined based on an eleventh syntax element indicating whether a picture partitioning is applied to the video picture. 
 
     
     
       9. The method of  claim 8 , wherein the value of the tenth syntax element is inferred to be equal to 1 when a value of the eleventh syntax element is equal to 1, wherein the value of the tenth syntax element being equal to 1 indicates that each of the one or more subpictures in the video picture includes the single slice, and wherein the value of the eleventh syntax element being equal to 1 indicates that no picture partitioning is applied to the video picture, or
 wherein the single slice indicates only one rectangular slice, or 
 wherein the video comprises one or more coded layer video sequences (CLVSs), and wherein the format rule further specifies that a list of target subpicture index values is used as an input for a subpicture sub-bitstream extraction process, wherein a manner of modifying a twelfth syntax element for determining an output sub-bitstream in the subpicture sub-bitstream extraction process is determined based on a subpicture index, wherein the manner of modifying the twelfth syntax element comprises rewriting or removing the twelfth syntax element, wherein each target subpicture index value and a subpicture identifier (ID) indicated by a thirteenth syntax element satisfy that SubpicIdVal[target subpicture index value] is equal to the subpicture ID, and wherein SubpicIdVal is a mapping function. 
 
     
     
       10. The method of  claim 1 , wherein the video picture includes one or more subpictures,
 wherein the conversion comprises determining an output sub-bitstream by extracting a sub-bitstream of one or more target subpictures from the bitstream during a subpicture sub-bitstream extraction process, and 
 wherein the format rule further specifies that in the output sub-bitstream, a fourteenth syntax element in all referred syntax structures of a sequence parameter set and a fifteenth syntax element in all referred syntax structures of a picture parameter set are modified to be equal to 0, and the fourteenth syntax element and the fifteenth syntax element indicate a number of subpictures in each of the video picture minus 1. 
 
     
     
       11. The method of  claim 10 , wherein in the output sub-bitstream, one or more values of a sixteenth syntax element referred to the one or more target subpictures in all output layers are equal to a first specific value, where the sixteenth syntax element indicates whether the one or more target subpictures of each video picture in a coded layer video sequence (CLVS) are treated as pictures in a decoding process excluding an in-loop filtering operation, wherein the first specific value is equal to 1, and the one or more values of the sixteenth syntax element equal to 1 indicates that the one or more target subpictures of each video picture are treated as pictures in the decoding process excluding the in-loop filtering operation, or
 wherein in the output sub-bitstream, one or more values of a seventeenth syntax element referred to the one or more target subpictures are equal to a second specific value, where the seventeenth syntax element indicates whether an in-loop filtering operation across boundaries of the one or more target subpictures is enabled, wherein the second specific value is 0, and the one or more values of the seventeenth syntax element equal to 0 indicates that the in-loop filtering operation across the boundaries of the one or more target subpictures is disabled. 
 
     
     
       12. The method of  claim 10 , wherein in the output sub-bitstream, one or more values of an eighteenth syntax element in the sequence parameter set referred to the output sub-bitstream of the one or more target subpictures are equal to a third specific value, where the eighteenth syntax element indicates whether an in-loop filtering operation is allowed to be performed across subpicture boundaries in a coded layer video sequence (CLVS) and whether all the subpicture boundaries in the CLVS are treated as picture boundaries, wherein the third specific value is 1, and the one or more values of the eighteenth syntax element equal to 1 indicates that the in-loop filtering operation across subpicture boundaries of the one or more target subpictures is disabled and all the subpicture boundaries of the one or more target subpictures are treated as the picture boundaries, or
 wherein the one or more target subpictures are indicated by a list of target subpicture index values, which is used as an input for the subpicture sub-bitstream extraction process, or 
 wherein the video comprises at least one coding block, and wherein the coding block is a root node of a prediction tree or a transform tree, and the prediction tree specifies a position and a size of a prediction block, and the transform tree specifies a position and a size of a transform block, wherein splitting information for chroma component and luma video component is allowed to be identical or to be different for the transform tree or the prediction tree. 
 
     
     
       13. The method of  claim 1 , wherein the video picture includes one or more subpictures;
 wherein the format rule further specifies that one or more syntax elements are constrained based on one or more constraint flags of general constraints information, 
 wherein the one or more constraint flags comprise a first constraint flag indicating whether each video picture in an output layer set contains only one slice, and the one or more syntax elements comprises a nineteenth syntax element present in each slice header of the output layer set which plus 1 indicates a number of tiles in a slice, and 
 wherein in case that the first constraint flag is equal to 1 and a twentieth syntax element indicating whether a rectangular slice is in use for each video picture is equal to 0, the nineteenth syntax element is constrained to be equal to a variable minus 1, where the variable indicates a number of tiles in the video picture, and wherein the first constraint flag being equal to 1 indicates that each video picture contains only one slice and the twentieth syntax element being equal to 0 indicates that the rectangular slice is not in use for each video picture. 
 
     
     
       14. The method of  claim 13 , wherein the one or more syntax elements further comprises a twenty-first syntax element which plus 1 indicates a number of rectangular slices in each video picture, and wherein the twenty-first syntax element is constrained to be equal to 0 in case that the first constraint flag is equal to 1 and the twentieth syntax element is equal to 1, and wherein the twentieth syntax element being equal to 1 indicates that the rectangular slice is in use for each video picture, or
 wherein the variable is constrained to be equal to 1 in case that a second constraint flag indicating whether each video picture in the output layer set contains only one tile is equal to 1, and the second constraint flag being equal to 1 indicates that each video picture in the output layer set contains only one tile, or 
 wherein the one or more constraint flags further comprise a third constraint flag indicating whether the video picture comprises only one subpicture and whether subpicture information is present, and the one or more syntax elements further comprise a twenty-second syntax element which plus 1 indicates a number of subpictures in the video picture, wherein the twenty-second syntax element is constrained to be 0 in case that the third constraint flag is equal to 1, and the third constraint flag being equal to 1 indicates that the video picture comprises only one subpicture and the subpicture information is not present. 
 
     
     
       15. The method of  claim 1 , wherein the conversion comprises encoding the video into the bitstream. 
     
     
       16. The method of  claim 1 , wherein the conversion comprises decoding the video from the bitstream. 
     
     
       17. An apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to:
 perform a conversion between a video comprising a video picture that includes a video slice and a bitstream of the video, 
 wherein the bitstream conforms to a format rule, and 
 wherein the format rule specifies that, in case a slice type of the video slice is P and a temporal motion vector prediction for the video picture is enabled, usage of reference picture resampling (RPR) for a reference picture in a specific collocated reference picture list is disabled, wherein the reference picture is indicated by a first syntax element, which specifies a reference index of a collocated picture used for the temporal motion vector prediction, 
 wherein the format rule further specifies that a value of first certain information in a slice header for the video slice indicates the collocated picture used for the temporal motion vector prediction is derived from a reference list 0 when the slice type of the video slice is P and a value of a third syntax element in a picture header of the video picture indicates that the temporal motion vector prediction is enabled for the video picture. 
 
     
     
       18. A non-transitory computer-readable storage medium storing instructions that cause a processor to:
 perform a conversion between a video comprising a video picture that includes a video slice and a bitstream of the video, 
 wherein the bitstream conforms to a format rule, and 
 wherein the format rule specifies that, in case a slice type of the video slice is P and a temporal motion vector prediction for the video picture is enabled, usage of reference picture resampling (RPR) for a reference picture in a specific collocated reference picture list is disabled, wherein the reference picture is indicated by a first syntax element, which specifies a reference index of a collocated picture used for the temporal motion vector prediction, 
 wherein the format rule further specifies that a value of first certain information in a slice header for the video slice indicates the collocated picture used for the temporal motion vector prediction is derived from a reference list 0 when the slice type of the video slice is P and a value of a third syntax element in a picture header of the video picture indicates that the temporal motion vector prediction is enabled for the video picture. 
 
     
     
       19. A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises:
 generating the bitstream of the video comprising a video picture that includes a video slice, wherein the bitstream conforms to a format rule, and 
 wherein the format rule specifies that, in case a slice type of the video slice is P and a temporal motion vector prediction for the video picture is enabled, usage of reference picture resampling (RPR) for a reference picture in a specific collocated reference picture list is disabled, wherein the reference picture is indicated by a first syntax element, which specifies a reference index of a collocated picture used for the temporal motion vector prediction, 
 wherein the format rule further specifies that a value of first certain information in a slice header for the video slice indicates the collocated picture used for the temporal motion vector prediction is derived from a reference list 0 when the slice type of the video slice is P and a value of a third syntax element in a picture header of the video picture indicates that the temporal motion vector prediction is enabled for the video picture.